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Aruba Employee
Posts: 509
Registered: ‎07-03-2008

RAP won't connect to backup LMS if RAP is rebooted

I'm fighting with a problem where I have two geographically diverse controllers in master/standby configuration. There's very specific reasons why they are master/standby and not master/local. Version = 6.1.0.0.

When I connect a RAP-5WN to the environment in steady-state, everything is fine, the RAP-5WN connects to the primary master, clients connect to the advertised SSID, traffic flows, etc. When I take down the master, the standby assumes master role and the RAP-5WN connects over to the standby. Again, client reconnects to the SSID, traffic flows, everything is fine.

However, if I reboot the RAP-5WN when the controllers are in this state, the RAP-5WN will not connect to the "backup" controller. It just sits there with the power light blinking, however my backup SSID is being advertised. If I bring the primary controller back up at this point, the RAP-5WN will connect to it.

Do I have a configuration issue or is this the behavior I can expect? Please don't tell me it's what I should expect.
Guru Elite
Posts: 20,960
Registered: ‎03-29-2007

Re: RAP won't connect to backup LMS if RAP is rebooted

The Backup LMS ip address is ONLY propagated after an AP finds an actual controller after rebooting. It is not stored on the AP. If an AP is only provisioned with the first controller's IP address, that is all that it can try. The best way to do "cold-boot" redundancy is to provision the AP with a dns name that is populated with two addresses.


Colin Joseph
Aruba Customer Engineering

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Aruba Employee
Posts: 509
Registered: ‎07-03-2008

Re: RAP won't connect to backup LMS if RAP is rebooted

Well, DNS is something at least. I'm still trying to figure out some kind of rationale for not storing the backup LMS, but nothing comes to mind. I think that should be a feature request.
Guru Elite
Posts: 20,960
Registered: ‎03-29-2007

Re: RAP won't connect to backup LMS if RAP is rebooted

DNS provides more flexibility than static ip addresses, just like the aruba-master entry. Very few people use static entries in campus WLAN; why should they in Remote APs?


Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

Aruba Employee
Posts: 509
Registered: ‎07-03-2008

Re: RAP won't connect to backup LMS if RAP is rebooted

Let me get this straight, in campus WLANs with a master/local configuration you would recommend people just use aruba-master as the primary LMS and don't bother with a backup LMS? Exactly how would that work?
Guru Elite
Posts: 20,960
Registered: ‎03-29-2007

Re: RAP won't connect to backup LMS if RAP is rebooted

Only if you need cold-boot site redundancy.


Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

Aruba Employee
Posts: 509
Registered: ‎07-03-2008

Re: RAP won't connect to backup LMS if RAP is rebooted

I don't even see how that's feasible in an enterprise environment. If I have 50 local controllers and a master, I can't list all the local controllers and the master in a DNS entry for aruba-master. Who knows what controller an AP is going to connect to.

All that hassle because Aruba won't propagate the backup LMS setting to an AP and have it survive a cold-boot? How much trouble could that actually be to implement?

So, if I lose a local controller at a site perhaps because of a power outage, their backup controller, the master, if useless to me because even though I have it in as the backup LMS, oh no, the APs rebooted?

DNS is providing flexibility where flexibility isn't needed. It actually makes life more difficult in a RAP scenario with a geographically diverse master/standby setup. I'm not saying not to use DNS for the master and for the standby, but to have to put both IP addresses in for a single DNS name so a RAP can survive a cold-boot doesn't seem right to me.
Aruba Employee
Posts: 99
Registered: ‎09-08-2010

Re: RAP won't connect to backup LMS if RAP is rebooted




Mike, in a large entrerprise environment with 50 controllers, DNS could point to the master controller pair, with the AP System profile pointing to the preferred LMS and Backup LMS IPs. The A record for Aruba-Master doesn't need to point to ALL controllers, it just needs to provide a bit of redundancy and point to more than one controller so that APs can survive a central controller failure.

In your case where you have geo redundancy, Aruba-Master would point to the two main geo sites, and from either of those two main controllers, an AP can learn of any/all available "local" controllers.

Guru Elite
Posts: 20,960
Registered: ‎03-29-2007

Re: RAP won't connect to backup LMS if RAP is rebooted

The access point only needs to contact ONE controller to be operational. It can then be redirected to wherever its home is, using LMS-IP and then to the Backup LMS-IP if that initial controller goes away. If you had to put in 2 ip addresses into 100 access points manually that would be onerous. To know what dns a-record they look for and just manipulate that to provide redundancy is much easier.


Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

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